#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/eventfd.h>

int main()
{
    int efd = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
    if (efd < 0) {
        perror("eventfd faild!");
        return -1;
    }

    uint64_t val = 1;
    write(efd, &val, sizeof(val));
    write(efd, &val, sizeof(val));
    write(efd, &val, sizeof(val)); 
    write(efd, &val, sizeof(val));
    uint64_t res;
    read(efd, &res, sizeof(res));

    printf("%lu\n", res);

    close(efd);

    return 0;
}